Multiplex system



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W. DI'HOUGHTON MULTIPLEX SYSTEM l/6J A STEPWAVE GEN l .SYNGPULSEGENERATOR .WEP 11m/E PULSE PULSE 650.3

Feb. 27, 1951 Filed March 28, 1947 CRYSTAL PULSE 05C l DELAY NETWOK/PDELAY NETWORK? R. o mw ET VH NG lU O H D. .M M .L u WIHIIIIIIIIIIIIIIIIIIIII? s 1234567891111101114161617512345616s/01112131415113175123 l1l1l1` ATTORNEY' Feb. 27, 1951 w. D. HOUGHTONMULTIPLEX SYSTEM 3 Sheets-Sheet 2 Filed March 28, 1947 INVENTOR. WILLIAMD HOUGHTON ATTORNEY Feb. 27, 1951 w. D. HouGHToN MULTIPLEX SYSTEM FilledMarch 28, 1947 1- J UNVENTOR. J

WILLIAM D. HouGHToN ATTORNEY Patented Feb. 27, 19514 UNITED STATESPATENT FFHCE poration of Delaware Applieatio Ma'cl 28, 1947, Serial No.737,901

y19 Claims. lk

This invention relates to multiplex or multichannel systems opera-tingon the time division principle, sometimes referred to as time divisionpulse multiplex systems.

In time division multiplex systems there is provided a distributor whichsequentially allots a common transmission medium to the differentchannel units. In systems involving a small number of channels (forexample,Y to 10 channels), the distributor may consist of a simple `stepvoltage wave generator to which the grids of all channel selector tubesare connected in parallel. The output from the step voltage wavegenerator appears as a series oi increasing steps or risers of voltage.The different channel selectors are differently biased to permit anodecurrent flow to start on dinerent steps or risers of the applied stepvoltage wave. The voltage increment for each riser in the step wavestarts the time interval allotted to one channel during which time thechannel may produce a modulated pulse. Each channel is allotted a timeinterval slightly shorter than the interval between succeeding steprisers on-the step voltage Wave. In vsuch a system, the maximum numberof channels is determined by the number of steps or risers in the stepWave generator output. A multiplex system of the type described above isdescribed in detail in my copending application, Serial No. 608,957, ledAugust 4, 1945, now U. S. Patent 2,531,817, issued November 28, 1950, towhich reference is herein made. Reference is also made to U. S. Patent2,413,440, granted December 31, 1946, to J. F. Farrington and to my U.S. Patent 2,480,137 for disclosures of systems utilizing a step Wavegenerator for controlling dine-rent channels on different step risers ofthe step voltage Wave.

When a very large number of channels is desired, a single step VoltageWave generator is not very practical since the voltage differential perstep or riser in the step voltage Wave becomes too small with reasonablevalues of supply voltage for the step Wave generator. culty, I proposein the present invention to use in a multiplex time division systemseveral step voltage Wave generators so arranged that the outputs fromthe different step wave generators are coupled to different groups ofchannels.

An object of my invention is to provide a simple method of generatinglarge numbers of equal time intervals for use in time division multiplexk systems.

Another object of the inventionis to so design a multiplex system thatgroups or lbanks of channels may be inserted or taken out of the system,

To overcome this difin accordance with installation requirements, in asimple 4and quick manner Without interfering with the operation of theother channels.

An advantage of the system of the invention involving multiple stepVoltage Waves is that the number of synchronizing pulses per frame iskept at a minimum in order to obtain the maximum time possible for theintelligence carrying channel pulses. Another advantage of the inventionlies in the fact that a master oscillator is employed Whose frequency ismaintained at a low value as a result of which the system permits theuse of one synchronizing pulse per frame or sampling cycle. Anotheradvantage of the invention resides inthe fact' that it provides a meansior generating multiple step voltage Waves which may be used either intransmitting or receiving multiplex equipment, and preferably in both.

A very brief description of the operation of the multiplex system of theinvention follows: A master pulse oscillator whose frequency is equal tofo/fg, where fo is the maximum repetition rate of the combined channelpulses and fg is the number of step Voltage Waves, is used to feed anumber of delay circuits. The number of delay circuits is made one lessthan the number of step voltage wave generators. The output from eachdelay circuit is used to produce a short pulse which drives anassociated step voltage Wave generator individual thereto. The pulsesfrom the master oscillator are also coupled to a step voltage wavegenerator which fires or discharges itself after the desired number ofsteps or risers, and at the same time discharges all other step voltagewave generators. The output from each step voltage wave generator iscoupled to a group of channels. A cathode output amplier may be used tocouple the step voltage wave generator to its associated group ofchannels. At the time of the discharge of all step wave generators, asynchronizing pulse is-generated which occupies the time intervalbetween the discharge and the next fol-lowing step riser. In this systemit is necessary to send only one synchronizing pulse per frame.

A more detailed description of the invention follows in conjunction witha drawing: wherein;

Fig. l diagrammatically illustrates, in box form, a multiplex systemoperating on the time division principle in accordance With theprinciples of the present invention;

Fig. 2 is a series of curves or voltage Wave forms given to explain theoperation 0i the invention;

Fig. 3 schematically illustrates details of some ofthe circuits shown inthe boxes of Fig. 1;

Fig. 4 is' a modification of the system of Fig. 3.

gereset Referring to Fig. 1 in more detail, this ligure showstransmitting equipment for 17 channels in accordance-with the invention.The number of channels has been selected as 17 merely for purpose ofexplanation, and it should be understood that any larger number ofchannels up to 100 channels more or less, can be used. A crystaloscillator A is employed to lock in a master pulse oscillator B. Theoutput from pulse oscillator B is coupled through lead I I to two phasedelaying networks C and D andfalso through lead III to step voltage wavegenerator G. The output from delay network C is used to drive a trippingpulse oscillator E over lead H2, and the output from delay network D isused to drive a tripping pulse oscillator F over lead H3. Phase delaynetworks C and D are shown as artificial lines of the lumped constanttype. The output pulses from pulse oscillators E and F are coupled toseparate step voltage wave generators H and I respectively, throughleads H4 and II5. The step voltage wave from generator G is coupled to agroup or bank K of 5 channels, while the outputs from the step wavegenerators H and I are coupled to two groups or banks L and M of sixchannels each. A synchronizing pulse generator J which produces asynchronizing pulse occurring immediately after the discharge of thestep wave generators G, H and I, is controlled by the step wavegenerator G over lead I I6. The combined channel pulses plus thesynchronizing pulse are coupled to the common amplifying equipment Nwhich combines the synchronizing pulse and the output pulses from thechannel banks and amplies the pulse train in preparation for modulatinga radio frequency transmitter 'I'. The synchronizing pulse generator Jis coupled to the amplifier equipment N through lead II'I, while thegroups of channels K, L and M are individually coupled to this sameamplifying equipment over leads II8, H9, and |20.

The crystal oscillator A produces a sine wave output whose positive ornegative portion controls the production of a pulse from the pulsegenerator B. The oscillator A may be any LC or an RS type depending uponstability requirements of the system. The pulse generators B, E and Fmay be identical in circuit design and may be blocking type pulseoscillators which produce identical D.-C. pulses at the same repetitionrate and at the frequency of the crystal oscillator A. The timeconstants of the pulse oscillators B, E and F are so chosen that theirnatural frequency of operation is slightly lower than the frequency ofcrystal oscillator A. Due to the time delays of networks C and D, thepulses produced by pulse oscillators B, E and F occur sequentially anddo not overlap. The time delay of network D is greater than the timedelay of network C.

When pulse oscillator B fires or produces a pulse, a pulse is sent outsimultaneously over leads IIIJ and III. The pulse 0n lead III willproduce a voltage rise in the step wave output from generator G. Thepulse on lead II will cause pulse oscillators E and F to produce pulseswhich result in rises in the voltage in the step wave outputs fromgenerators H and I, but at different occurrence times which are afunction of the time delays of networks C and D.

The pulse oscillators B, E and F are in effect, wave shapers to assureidentically shaped pulses being applied to generators G, H and I. If thenetworks C and D do not unduly distort the 4 waveform of the pulsespassed therethrough, then pulse oscillators E and F can be omitted.

When the peak or total amplitude of the step voltage wave produced bystep wave generator G exceeds a predetermined value, it causes adischarge of the generator G and, by virtue of connections I2I and |22,also causes a discharge of step wave generators H and I.

The individual channels in each group or bank K, L and M have channelselectors which are dilerently biased to become selectively eifective oroperative on different voltage steps or risers of the step voltage waveproduced by the associated step wave generator G, H or I respectively.All channel selectors in any one bank or group have their inputelectrodes fed in electrically parallel relationship by the step voltagewave applied thereto. The channel selectors may be of the type describedin my copending application, Serial No. 608,957, now U. S. Patent2,531,817. Each channel in a group or bank has a modulation circuitindividual thereto. All of the pulse outputs from a group or bank K, Lor M are combined and fed to the common output lead IIB, H9 or |20.

The pulses in the output of amplifying equipment N are fed over a lineTL for frequency modulating or keying a suitable radio frequencyoscillator T, such as a Klystron, or a magnetron. The resultantmodulated signal in the output of oscillator T is' fed to an antenna orwave directive structure |25.

Referring to Fig. 2, curves or waveforms a, b and c graphicallyrepresent sequentially occurring pulses produced by pulse oscillators B,E

and Fy respectively. The voltage wave forms shown in curves d, e and fof Fig. 2 represent the step voltage waveforms produced by step wavegenerators G. H and I, respectively. rIhe pulses shown in curve y ofFig. 2 represent the combined pulses in succeeding frames as they appearin the output of the common amplifying equipment N. The synchronizingpulse in curve g is identified by the letter S, while the channel pulsesare represented by the numerals I to II, for the assumed case of 17channels. It should be noted that the synchronizing pulse S is shownWider than any of the intelligence carrying channel pulses. These pulsesfrom the output of amplifying equipment N may be either time oramplitude modulated, depending upon the type of circuits employed in theindividual channels in groups or banks K, L and M, or a combination ofboth types of modulation may be used simultaneously, if desired.

Fig. 3 shows, schematically, the essential details of the apparatus ofthe invention which may be employed in Fig. l. The dashed line boxes inFig. 3 respectively include the equipment indicated by those in Fig. 1which have the same reference characters.

Referring to Fig. 3 in more detail, the pulse oscillator B is aconventional transformer feedback blocking oscillatorv whcse normalfrequency is slightly lower than the frequency of the controllingoscillator A. The crystal oscillator vacuum tube 5I is a triode typetube having a controlling crystal 55, and provided with a resistor 52 inits cathode circuit. A positive pulse is developed across this resistorwhen the sine wave on the grid of 5I reachesits maximum positive value.The cathode resistor 52 also forms part of the grid leak resistors inthe grid circuit of the pulse oscillator tube. The positive pulse tripsthe pulse oscillator B at the crystal frequency. Pulses of positivepolarity are developed across cathode resistor S in the pulse oscillatorB, and these pulses are coupled tothe two delay lines C and D as shown.Delay line D is vterminated by a resistor whose value is equal to thesurge impedance of the line, to thereby prevent reflection of wavestraveling down the line. Although two delay lines only are shown, hisnumber of delay lines will provide satisfactory operation with a numberof channels up to 30, but for more than 30 channels more delay linesshould be used.

The pulses from delay line C are taken off from point X and are used totrip a pulse oscillator E, while the pulses `from the end of the delayline D are taken on" point Y and are used to trip pulse oscillator F.The pulse oscillators E, F and B are identical in construction, as aresult of which there are produced three sets of identical pulses in themanner shown by curves c, b and c of Fig. 2. It should be noted from aninspection of Fig. 2 that a pulse from pulse oscillator B is followed bya pulse from pulse oscillator EL which is spaced in time by one-thirdlthe time period between adjacent pulses from pulse oscillator B.Similarly, a pulse. from pulse oscillator E is followed by a pulse frompulse oscillator F which is spaced in time by one-third the time periodbetween adjacent pulses from B.

The pulses from pulse oscillator B drive the step voltage wave generatorG. The operation of pulse generator G may be summed up as follows:Vacuum tube l l is biased to be normallynon-conducting due to the gridleak bias developed across resistor 8. Each positive pulse from pulseoscillator B- overcomes the bias on tube IE and causes it to becomeconducting for the duration of this pulse, during which time a charge isstored in condenser l resulting in a rise in voltage on this condenser.After the end of the pulse from oscillator B, current ceases to flow intube I i and, since no resistance is present across condenser It thepotential previously developed on this condenser remains thereon. Uponthe occurrence of the next pulse from pulse oscillator B, the condenserl@ is charged to a higher potential. This action continues to build upincrements oi:` increasing potential on condenser it until the totalpotential across condenser m exceeds the bias on tripping oscillatorvacuum tube i3. The amount of incremental charge stored in condenser Itfor each pulse from oscillator B is a function of the duration of thepulse from oscillator B, the anode-cathode impedance oi tube li and thevalues of anode resistor s and condenser lil. The values of resistor Qand condenser l!) are chosen so that there is obtained a desiredamplitude of step riser across condenser it for each pulse fromosciliator B. Tripping oscillator vacuum tube i3 is biased by means of acathode resistor le and a bypass condenser l5. The transformer I2 hasits windings so poled that when tube I3 starts to carry current, thevoltage on the grid of tube i3 is increased, resulting in an increasedcurrent. This action continues until condenser l0 is discharged by thegrid current from tube i3 at which time tube it ceases to conduct andanother step wave voltage starts. The step wave voltage developed acrosscondenser Ii) appears as shown in curve d of Fig. 2, and is coupled to agroup K of 5channel units by means of cathode output amplifier it.Amplier I6 is here used as a cathode follower tube and permits thepassage therethrough of the step wave voltage as it is built up oncondenser l0. Resistor I1 in the cathode circuit of tube I6 is a groundreturn element.

The pulses from pulse oscillator E are coupled to a normallynon-conducting vacuum tube 25 in step wave generator H, and the pulsesfrom pulse oscillator F are coupled to normally nonconductive vacuumtube 38 in step wave generator I.- Tubes 25 and 38 operate in a mannersimilar to that described for vacuum tube Il ofv step wave generator G.Tube 25 charges condenser 28, while tube 38 charges condenser 3l, whenthese tubes become conductive. The anode of a normally non-conductingvacuum tube 2'! is connected to the cathode end of condenser 28, and asimilar vacuum tube 39 has its anode coupled to the cathode end ofcondenser 3l. The grids of tubes t9 and 2l are coupled via lead |33 toone end of winding W of transformer I2. negativen-C. potentialrepresented by the symbol -C is connected to the other end of thewinding W and is of suiiicient magnitude to maintain tubes 21 and 39 inthe anode current cut-oit condition. Other types oi bias such as gridleak or cathode bias may be applied to tubes 2l and 39 to replace the Cvoltage, if desired. The winding W of transformer i2 is so poled thatwhen tube I3 res (conducts), a' positive pulse is developed on the gridsof tubes 2l and 3s, causing these tubes to conduct and dischargecondensers 28 and 3l' respectively.

The action of the system with time then is as follows: Pulse oscillatorB fires, causing a step of voltage to be developed across condenser l0of generator G and also starting a pulse on delay line C. When the pulsetraveling along delay line C reaches point X, pulse oscillator E iires,causing a step of voltage to be developed across condenser 28 or stepwave generator H. The pulse on the delay line C continues to travel todelay line D, and when this pulse reaches the end of delay line Drepresented by point Y, pulse oscillator 1T' hres, causing a step ofvoltage to be developed across condenser 3'! ci step wave generator I.The time required for the pulse to travel from pulse oscillator B topoint X is equal to one-'third the time period between successive pulsesfrom oscillator B; and the time required 'for the pulse to travel frompoint X to point Y at the end of the delay line D is also one-third theperiod between successive pulses from pulse oscillator B. On the nextpulse from pulse oscillator B, condenser lil receives another charge,resulting in a step of voltage being stored thereon. The previouslydescribed action continues until tube I3 fires, at which time condensersIii, 28 and 3l are discharged and a nev.7 step voltage wave cycle isstarted.

VIt should be noted that the Vparticuiar pulse from oscillator B whichcaused the discharge of the step wave generators G, H and I continues totravel down the delay line C after this discharge and reaches point X ata time after the discharge which is equal to one-third the period ofoscillator B. This pulse at point X trips pulse oscillator E andproduces the first incremental charge in condenser 28 of step voltagewave generator H in the new step wave cycle. rEhe pulse on delay line Ccontinues to travel down line D and reaches point Y to trip pulseoscillator F and produces the first incremental charge in condenser 3lof step voltage wave-generator I in the new step wave cycle for thisgenerator. After the pulse reaches point Y, and at a time i intervalequal to one-third the period of oscillator B, the oscillator B againres, resulting in the first incremental charge in condenser I of stepvoltage wave generator G in the new step wave cycle for this generator.

The step Voltage waveforms from generators G, H and I appear as seen incurves d, e and f respectively of Fig. 2, and are taken oif the cathodesof cathode followers i6, 29 and 40 respectively.

The individual channel circuits of groups or banks K, L and M have notbeen shown but these may take the form of the circuits shown in mycopending application Serial No. 608,957, now U. S. Patent 2,531,817,referred to above. Each channel circuit may include the followingapparatus; a position or channel selector, a sawtooth generator, a pulsegenerator ancla pulse position modulator for varying the position of thepulse generated by the pulse generator in accordance with the amplitudeof the modulating signal for that channel. The channel selectors arealso 'shown in U. S. Patent 2,469,066, granted May 3, 1949, to J. R.Day. The different channel selectors in any one bank or group arenormally non-conductive Vacuum tubes which are differently biased tobecome conductive on different steps or risers of the step voltage waveapplied to the inputs of the channel selectors in parallel. Instead of apulse position modulator, each channel circuit may have an amplitudemodulator for modulating the amplitude or a pulse with modulator formodulating the length or duration of the pulse generated in the channel.

It should be further noted that although there are six risers in each ofthe step voltage wave outputs from generators G, H and I, as seen froman inspection of voltage wave forms d, e, and f, Fig. 2, there are onlyve risers allotted to ve channels in curve d whereas there are sixrisers allotted to six channels in each of curves e and f. The sixthriser in curve d starts the discharge action for all step wavegenerators. Each channel is allotted a time interval equal to one-thirdthe period of the pulses from B, In present practice, if the system isused with pulse position modulation there will be a guard space betweenchannels as described in my copending application, now U. S. Patent2,531,817, hereinbefore referred to, and the resultant output from thecommon ampliiier equipment N will be used to key on and olf the radiotransmittery T. If pulse amplitude modulation is employed, then thereshould be allotted suicient space between pulses from adjacent channelsto prevent undesired cross-modulation, and the resultant output pulsesfrom the amplifier N can be used to frequency modulate the radiofrequency transmitter T. The output from radio frequency transmitter T,in this last case, may be a single frequency modulated carrier wave, ora doubly frequency modulated carrier wave if a subcarrier is firstfrequency modulated and used to frequency modulate a higher frequencycarrier.

The synchronizing pulse may be generated by the discharge pulse from thestep wave generator G in a manner similar to that shown in my copendingapplication Serial No. 608,957, now U. S. Patent 2,531,817. Thisdischarge pulse causes a normally conducting vacuum tube, called thesynchronizing pulse generator J to cut-off for a predetermined intervalof time greater than the time duration of a channel pulse. Thissynchronizing pulse occurs immediately after the discharge of the stepwave generators and before the next channel pulse, as will be seen froman inspection of curve g, Fig. 2, in which the channel pulse is labeledS. Of course two pulses more closely spaced than any adjacent channelpulses may be used, if desired, as synchronizing pulses, or thesynchronizing pulse may have an amplitude higher than that reached byany channel pulse on the extremes of modulation. If desired, thesynchronizing pulse generator may comprise any suitable vacuum tubecircuit well known in the multiplex or television arts for producing apulse of fixed width of Fig. 2. As an illustration of the manner inwhich both synchronizing and channel pulses are generated and combinedin a common amplifying equipment in a pulse multiplex system, referenceis made to U. S. Patent 2,403,210, granted July 2, 1946, to Butement etal.

The common ampliiier equipment N may take any suitable form, such asillustrated and described in my copending application Serial No.608,957, now U. S. Patent 2,513,817 referred to above.

Fig. 4 shows a modification or alternate circuit which may be usedinstead of the circuit of Fig. 3. The same reference charactersrepresent the same parts throughout both Figs. 3 and 4, while equivalentparts have been given prime designations in Fig. 4. In Fig- 4, thecrystal oscillator is shown as A and the output of this crystaloscillator locks in the pulse oscillator B at the frequency of thecrystal oscillator. The output of the pulse oscillator B is used tocontrol a saw-tooth voltage generator P which generates a saw-toothvoltage wave whose linear rise time is equal to the time betweenadjacent pulses from pulse oscillator B'. Phase delay networks C and Dreplace the delay lines C and D of Fig. 3. The saw-tooth generator Pcomprises a vacuum tube |33 which is normally non-conducting and aresistor |50 and a condenser |5| in its anode circuit. The applicationof a pulse from pulse oscillator B will cause tube |33 to conduct anddischarge the condenser |5| which had charged linearly during thenon-conductive period of tube |33 corresponding to the period betweenpulses from B. Phase delay networks C and D each comprise a normallynon-conductive vacuum tube |21 and |53 respectively. Pulse generators Eand F of Fig. 4 are identical with pulse generators E and F of Fig. 3except that they are driven from their anode circuits instead of theirgrid circuits, as shown. Tube |21 of this delay network C is so biasedthat it becomes conducting at one-third the amplitude of the appliedsaw-tooth voltage wave from sawtooth generator P. When tube |21 becomesconducting, a current change takes place in transformer |38 of pulsegenerator F', causing pulse oscillator E to fire, Hence a pulse isgenerated by pulse oscillator E at a time equal to one-third the timeperiod of pulse oscillator B after pulse oscillator B fires. Tube |43 ofphase delay network D is similar to |21 of network C' with the exceptionthat it is biased to become conducting at a time equal to two-thirds thetime period of pulse oscillator B after B res. Tube of step wavegenerator G of Fig. 4 is driven by means of a transformer in the cathodecircuit of tube 1 of the pulse oscillator B instead of from thetransformer in the anode circuit of pulse oscillator B as shown in Fig.3. Except for the foregoing, the system of Fig. 4 operates in a mannesimilar to that described for Fig. 3. Y.

The present invention provides a simple means of generating the largenumbers of timing intervals for use in a time division multiplex system.The frequency vof the master oscillator may be kept at a low value thuspermitting the use fof f one synchronizing pulse per frame or samplingcycle. An important feature of the invention is that different groups orbanks of channels may be built as units which can be added to the Isys--tem or taken out from the system according to installation requirements,in a quick and simple manner.

It should be understood of course that an additional step wave generatoridentical with I-I and I can be included in the circuit of Fig. 3 andused in similar manner, with an additional section of delay network atthe bottom of network D feeding this additional step wave generator.Another counter circuit could then be used only to discharge all thestep wave generators.

What is claimed is:

1. In a multi-channel communication system wherein a common transmissionmedium is sequentially assigned to the diierent channels, a source ofcontrolling repetitive waves, a plu-` rality of step voltage wavegenerators, circuits having different phase delays coupling said sourceto said generators, each of said generators producing a step voltagewave having a plurality of risers of different voltage values, saidphase delays being so related as to cause the risers in the step voltagewave produced by one generator to be interlaced with the risers in thestep voltage wave produced by another of said generators.

2. In a multi-channel communication system wherein a common transmissionmedium is sequentially assigned to the different channels, a source ofcontrolling repetitive waves, a plurality of step voltage wavegenerators, circuits having different phase delays coupling said sourceto said generators, each of said generators producing a step voltagewave having a plurality of risers of diierent voltage values, each stepor riser in the voltage wave produced by any one generator occurring inthe interval between adjacent steps or risers of the voltage wavesproduced by the other generators, whereby said steps or risers in all ofsaid voltage waves are interlaced, and means in circuit with all of saidstep wave generators and responsive to a predetermined voltage valuedeveloped by one of said step wave generators for discharging all ofsaid step wave generators.

3. In a multi-channel communication system wherein a common transmissionmedium is sequentially assigned to the different channels, a source ofcontrolling repetitive waves, a plurality of step voltage wavegenerators, circuits having diierent phase delays coupling said sourceto said generators, each of said generators producing a step voltagewave having a plurality of risers of different voltage values each stepor riser in the voltage wave produced by any one generator occurring inthe interval between adjacent steps or risers of the voltage wavesproduced by the other generators, whereby said steps or risers in all ofsaid voltage waves are interlaced, one of said step wave generatorsincluding a normally non-conductive pulse oscillator responsive to apredetermined voltage developed by said one step wave generator fordischarging the same, and connections from said pulse oscillator to theother step wave generators for discharging said other generators whensaid pulse oscillator produces a pulse.

4. A multi-channel communication system comprising a iirst pulseoscillator, a second pulse oscillator, a phase delay circuit couplingthe output of said first oscillator to the input of said secondoscillator, whereby said nrst oscillator exercises control over saidsecond oscillator through said delay circuit, separate step voltage wavegenerators individually coupled to and under control of said pulseoscillators, each `of said step voltage wave generators producing a wavehaving a plurality of risers of dilerent voltage values, eachincremental change in voltage produced in one step wave generatoroccurring in the interval between adjacent incremental changes involtage produced in the other step wave generators whereby saidincremental changes in all of said step voltage waves are interlaced.

5. A multi-channel communication system comprising a first pulseoscillator, a second pulse oscillator, a phase delay circuit, meanscontrolling said second oscillator from said rst oscillator through saiddelay circuit, said pulse oscillators being so constructed and arrangedas to produce pulses of substantially identical characteristics,separate step Voltage wave generators individually coupled to and undercontrol of said pulse oscillators, each of said step voltage wavegenerators producing a wave having a plurality of risers of diierentvoltage values, each step or riser in the voltage wave produced by anyone generator occurring in the interval between adjacent steps or risersof the voltage waves produced by the other generators, whereby saidsteps or risers in all of said voltage waves are interlaced.

6. A multi-channel Communication system comprising a rst pulseoscillator, a second pulse oscillator, a phase delay circuit, meanscontrolling said second oscillator from said iirst oscillator throughsaid delay circuit, separate step voltage wave generators respectivelycoupled to and under control of said pulse oscillators, each of saidstep voltage wave generators producing a wave having a plurality ofrisers of diierent voltage values, each step or riser in the voltagewave produced by any one generator occurring in the interval betweenadjacent steps or risers of the Voltage waves produced by the othergenerators, whereby said steps or risers in all of said voltage wavesare interlaced, a group of channel circuits having their inputs coupledin electrically parallel relation to one of said step voltage wavegenerators, another group of channel circuits having their inputscoupled in electrically parallel relation to the other step voltage wavegenerator, means in circuit with the channel circuits in each group fordifferently biasing the channel circuits to become effective ondifferent risers of the step voltage wave applied to said group.

7. In a multi-channel communication system wherein a common transmissionmedium is sequentially assigned to the dilerent channels, a source ofcontrolling repetitive waves, a plurality of step voltage wavegenerators, circuits having' different phase delays coupling said sourceto said generators, each of said generators producing a step voltagewave having a plurality of risers of different voltage values, each stepor riser in the voltage wave produced by any one generator occurring inthe interval between adjacent steps or risers of the voltage wavesproduced by the other generators, whereby said steps or risers in all ofsaid voltage waves are interlaced, and means in circuit with all ofsaidstep wave generators and responsive to a predetermined voltage valuede- 'l yeloped by one of said step wave generators for discharging allof said step wave generators, a group of channel circuits having theirinputs coupled in electrically parallel relation to one of said stepvoltage wave generators, another group of channel circuits having theirinputs coupled in electrically parallel relation to the other stepvoltage wave generator, and means in circuit with the channel circuitsin each group for differently biasing the channel circuits to becomeeffective on diierent risers of the step voltage wave applied to saidgroup. v

8. The method of operating a multi-channel communication system whichincludes, producing a plurality of step voltage waves each having aplurality of risers of different voltage values, phase displacing saidstep waves such that any one riser in one wave occurs at a time intervalbetween an adjacent pair of risers in another step wave, whereby therisers in the different step waves are interlaced, and controllingdifferent channel circuits from the different risers.

9. The method of operating a multi-channel communication system whichincludes, producing a plurality of step voltage waves each having aplurality of risers of different voltage values, phase displacing saidstep waves such that any one riser in one wave occurs at a time intervalbetween an adjacent pair of risers in another step Wave, whereby therisers in the different step waves are interlaced, causing the differentphase displaced risers to produce different phase displaced pulses, andcontrolling a radio frequency wave from said pulses.

10. The method of operating a multi-channel communication system whichincludes, producing a plurality of step voltage waves each having aplurality of risers of different voltage values, phase displacing saidstep waves such that any one riser in one wave occurs at a time intervalbetween adjacent risers in another step wave, whereby the risers in thedifferent step waves are interlaced, utilizing the different phasedisplaced risers to produce different correspondingly positionedamplitude modulated pulses, feeding said pulses to a common radiofrequency oscillator, and modulating the frequency of said oscillator bysaid pulses.

11. A multi-channel communication system comprising a first pulseoscillator, a second pulse oscillator, a phase delay circuit, meanscontrolling said second oscillator from said rst oscillator through saiddelay circuit, individual step voltage wave generators coupled to andunder control of said pulse oscillators, each of said step voltage wavegenerators producing a wave having a plurality of risers of differentvoltage values, each step or riser in the voltage wave produced by anyone generator occurring in the interval between adjacent steps or risersof the voltage waves produced by the other generators, whereby saidsteps or risers in all of said voltage waves are interlaced, a group ofchannel circuits having their inputs coupled in electrically parallelrelation to one of said step voltage wave generators, another group ofchannel circuits having their inputs coupled in electrically parallelrelation to the other step voltage wave generator. and means in circuitwith the channel circuits in each group for differently biasing thechannel circuits to become effective on different risers of the stepvoltage wave applied to said group.

12. A multi-channel communication system comprising a first pulseoscillator, a second pulse oscillator, a phase delay circuit, meanscontrolling said second oscillator from said rst oscillator through saiddelay circuit, separate step voltage wave generators respectivelycoupled to and under control of said pulse oscillators, each of saidstep voltage wave generators producing a wave having a plurality ofrisers of different voltage values, the risers in the different stepvoltage waves being phase displaced in dependence upon the constants ofsaid delay circuit, each step or riser in the voltage wave produced byany one generator occurring in the interval between adjacent steps orrisers of the voltage waves produced by the other generators, wherebysaid steps or risers in all of said voltage waves are interlaced, meansin circuit with all of said step wave generators and responsive to apredetermined voltage value developed by one step wave generator forsimultaneously terminating the step voltage waves of all step wavegenerators, a synchronizing pulse generator controlled by said means toproduce a pulse upon the termination of said step waves and in theinterval between step voltage waves, a plurality of channel circuitscoupled to each of said step voltage wave generators and biased tobecome responsive to different risers on the step voltage waves toproduce different phase displaced pulses, and common amplifyingequipment coupled to the outputs of said channel circuits and to saidsynchronizing pulse generator.

13. A multi-channel transmitting system comprising a source of pulses ofconstant repetition rate, a delay network, a pair of pulse oscillatorscoupled to different points on said delay network, means coupling saidsource to said network, whereby said source controls said pulseoscillators through said delay network, the arrangement of said delaynetwork being such that one pulse oscillator is controlled by saidsource before the other pulse oscillator, a step voltage wave generatorcoupled to and controlled by each pulse oscillator, each generatorproducing a step volt age wave having a plurality of risers of differentvoltage values, each step or riser in the voltage wave produced by anyone generator occurring in the interval between adjacent steps or risersof the voltage waves produced by the other generators, whereby saidsteps or risers in all of said voltage waves are interlaced, means incircuit with both step wave generators and responsive to a predeterminedvoltage value developed by one step wave generator for simultaneouslyterminating the step voltage waves produced by both step wavegenerators, a group of channel circuits coupled to each step wavegenerator and biased to become responsive to different risers in thestep voltage wave applied thereto for producing phase displaced pulses,said means being utilized to produce a synchronizing pulse, and a commonoutput circuit for all of said channels and for said synchronizingpulse.

14. In a multi-channel communication system wherein a commontransmission medium is sequentially assigned to the different channels,a source of controlling repetitive waves, a plurality of step voltagewave generators, circuits having different phase delays individuallycoupling said source to said generators, said circuits comprisingartificial lines of the lumped constant type, each of said generatorsproducing a step voltage wave having a plurality of risers of differentvoltage values, each step or riser in the voltage wave produced by anyone generator occurring in the interval between adjacent steps or risersof the voltage waves produced by the other generators, whereby saidsteps or risers in all of said voltage waves are interlaced, and meansresponsive to a 13 predetermined voltage value developed by one of saidstep Wave generators for discharging all of said step Wave generators.

15. In a multi-channel communication system wherein a commontransmission medium is sequentially assigned to the different channels,a source of controlling repetitive waves, a plurality of step voltagewave generators, means individually coupling said generators to saidsource and assuring different phase delays in the operation of saidgenerators, said means including a sawtooth voltage generator and anormally non-conductive tube between said saw-tooth generator and eachone of said respective generators, and means in circuit with saidnormally non-conductive tubes for biasing said tubes to becomeconducting on different portions of the rise of the saw-tooth voltagewave, each of said generators producing a step voltage wave having aplurality of risers of different voltage values, each step or riser inthe voltage Wave produced by any one generator occurring in the intervalbetween adjacent steps or risers of the voltage waves produced by theother generators, whereby said steps or risers in all of said voltagewaves are interlaced.

16. The method of operating a communication system which includesproducing a substantially constant frequency repetitive Waveform,producing a pulse under control of each cycle of said repetitivewaveform, producing saw-tooth voltage waves under control of saidpulses, and producing under control of said saw-tooth voltage waves astep voltage Wave having a plurality of risers each of which representsone cycle of voltage produced by a saw-tooth voltage wave.

17. The method of operating a multi-channel communication system whichincludes, producing a plurality of time displaced step voltage Waveseach of which has a plurality of risers of different voltage values, thetime displacement being such that any one riser in one step wave occursat a time interval between a pair of adjacent risers in another stepwave, whereby the risers in the step Waves are interlaced, and producingfrom the different risers single polarity time displaced pulses in thechannel circuits, ap-

plying diierent modulating signals to the different channel circuits,thereby producing a series of pulses each bearing a different modulationfor each cycle of operations.

18. A method of operating a multi-channel communication system whichincludes, producing a plurality of phase displaced and interlaced stepvoltage Waves each of which has a plurality of risers of differentVoltage values, the phase displacement being such that any one riser inone step wave occurs at a time different from and between the risers inanother step wave, controlling different channel circuits from thedifferent risers in the different step voltage waves, producing pulsesin said channel circuits, and respectively modulating the pulsesproduced in different channel circuits by diiferent intelligence Waves.

19. In combination, a plurality of generators producing step voltageWaves each wave having a plurality of risers, means for applyingcontrolling repetitive waves to said generators through circuits havingdifferent phase delays, said phase delays being so related as to causethe risers in the step voltage Wave produced by one generator to beinterlaced With the risers in the step voltage Wave produced by anotherof said generators.

WILLIAM D. I-IOUGH'I'ON.

REFERENCES CITED The following references are of record in the le ofthis patent:

UNITED STATES PATENTS Number Name Date 2,113,011 White Apr. 5, 19382,199,634 Koch May 7, 1940 2,405,231 Newhouse Aug. 6, 1946 2,405,239vSeeley Aug. 6, 1946 2,413,440 Farrington Dec. 31, 1946 2,429,631 LabinOct. 28, 1947 2,468,059 Grieg Apr. 26, 1949 2,500,863 Posthumus 2- Mar.14, 1950

